Zeolites are crystalline aluminosilicate compositions which are microporous and which are formed from corner sharing AlO2 and SiO2 tetrahedra. Numerous zeolites, both naturally occurring and synthetically prepared, are used in various industrial processes. Synthetic zeolites are prepared via hydrothermal synthesis employing suitable sources of Si, Al and structure directing agents such as alkali metals, alkaline earth metals, amines, or organoammonium cations. The structure directing agents reside in the pores of the zeolite and are largely responsible for the particular structure that is ultimately formed. These species balance the framework charge associated with aluminum and can also serve as space fillers.
Zeolites are characterized by having pore openings of uniform dimensions, having a significant ion exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal without significantly displacing any atoms which make up the permanent zeolite crystal structure. Zeolites can be used as catalysts for hydrocarbon conversion reactions, which can take place on outside surfaces as well as on internal surfaces within the pore.
Zeolites having the NES framework type have a two-dimensional pore system with the approximate dimensions 4.8×5.7 Å (Ch. Baerlocher et al. “Atlas of Zeolite Framework Zeolite Types,” Sixth Revised Edition, Elsevier, 2007). An example of a zeolite having the NES framework type is NU-87. U.S. Pat. No. 5,102,641 discloses NU-87 and its synthesis using a polymethylene alpha, omega-diammonium cation as a structure directing agent.
U.S. Pat. Nos. 5,254,514 and 5,641,393 disclose zeolite SSZ-37 and its synthesis using an N,N-dimethyl-4-azoniatricyclo[5.2.2.0(2,6)]undec-8-ene cation as a structure directing agent. The structure of SSZ-37 has not yet been finally established, but it appears to be related to NU-87 (Y. Nakagawa, Stud. Surf. Sci. Catal. 1994, 84, 323-330), so that for the purposes of this disclosure, SSZ-37 should also be included among the zeolites having the NES framework type.
It has now been found that NES framework type zeolites can be prepared using a colloidal aluminosilicate composition in the presence of an N-cyclopentyl-N-methylpyrrolidinium cation as a structure directing agent.